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<title>Qucs - Matching Circuits</title>
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<center><h3>
- Qucs -<br>
Quite Universal Circuit Simulator<br>
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<h1>
Matching Circuits<br><br>
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Creating matching circuits is an often needed task in microwave
technology. Qucs can do this automatically. These are the
neccessary steps:<br>
<lu>
<li>Perform an S-parameter simulation in order to calculate the
reflexion coefficient.</li>
<li>Place a diagram and display the reflexion coefficient (i.e.
S[1,1] for port 1, S[2,2] for port 2 etc.)</li>
<li>Set a marker on the graph and step to the desired frequency.</li>
<li>Click with the right mouse button on the marker and select
"power matching" in the appearing menu.</li>
<li>A dialog appears where the values can be adjusted, for example
the reference impedance can be chosen different from 50 ohms.</li>
<li>After clicking "create" the page switches back to the schematic
and by moving the mouse cursor the matching circuit can be placed.</li>
</lu>
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The left-hand side of the matching circuit is the input and the
right-hand side must be connected to the circuit.
<br>
If the marker points to a variable called "Sopt", the menu shows the
option "noise matching". Note that the only different to "power matching"
is the fact that the conjugate complex reflexion coefficient is taken.
So if the variable has another name, noise matching can be chosen by
re-adjusting the values in the dialog.
<br>
The matching dialog can also be called by menu (Tools->matching circuit)
or by short-cut (&lt;CTRL-5&gt;). But then all values has to be entered
manually.
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<h3>
2-Port Matching Circuits<br>
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If the variable name in the marker text is an S-parameter, then an option
exists for concurrently matching input and output of a two-port circuit.
This works quite alike the above-mentioned steps. It results in two
L-circuits: The very left node is for connecting port 1, the very right
node is for connectiong port 2 and the two node in the middle are for
connecting the two-port circuit.
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